The present invention provides a systems and methods to perform an electrical test on a substrate assembly used as a TFT array substrate of a liquid-crystal device without detaching a mounted external IC. The substrate assembly can include a substrate, a peripheral circuit embedded in the substrate, a first wiring arranged on the substrate, and an external IC, mounted on the substrate, and having a first terminal connected to an interconnection portion arranged on the first wiring. The substrate assembly can further include a second wiring which extends from the interconnection portion in such a manner that the second wiring is routed in a portion of the substrate facing the integrated circuit, and a first external circuit connection terminal arranged on the second wiring in a portion of the substrate not facing the integrated circuit. The external IC is thus tested through the external circuit connection terminal.